Many dental procedures are made less painless and more efficient by the use of dental tools that employ a small volume of water, which is injected into a patient's mouth. For example, high-speed handpieces used for intra-oral drilling and grinding are typically cooled by a small stream of water, thereby minimizing at least some of the discomfort produced by heat that is generated thereby. Even simple cleaning procedures that produce bits of scale and tartar require that the debris be flushed from the work site and expectorated from the mouth with water injected through an air/water syringe. Ultrasonic scaling equipment also employs water injected into a patient's mouth. The source of the water used in each of these devices is normally city tap water that is conveyed from a dental workstation to the dental tool through an elastomeric or flexible plastic line. Although a city tap water supply may be chlorinated to disinfect it when drawn from the city's reservoir or storage tank, the water is not sterile when it is delivered to the patient's mouth.
Investigation has revealed that a biofilm often is present along the inner surface of the elastomeric plastic water line used to convey water from the dental workstation to a dental tool. Water flowing through this line develops a relatively high bacterial count by picking up bacteria from the biofilm. Because it is not unusual for dental procedures to cause bleeding in a patient's mouth, there is thus a high probability that the bacteria from the biofilm in the water line will enter a patient's blood stream. In healthy individuals, a small infusion of bacteria may not be cause for concern, since their bodies' natural immune systems can deal with the infection. However, people who are weakened because of prior or current health problems are particularly susceptible to illness caused by such bacteria. In fact, even healthy people can be infected and become ill due to exposure to the very high bacterial counts often found in water delivered through dental tool water lines. As noted in a study done by Chris Miller, Ph.D., described in an article entitled Infection Control 91 Report, pp. 92-93, Dental Products Report, September 1991, the bacteria found in the water lines include a number of potentially harmful nosocomial disease agents, including Legionella pneumophila, Pseudomonas aeruginosa, Pseudomonas cepacia, Flavobacterium spp, Mycobacterium chelonae, Acinetobacter spp, Klebsiella pneumoniae, and Acanthamoeba.
While it is possible to sterilize a dental tool water line with a sterilizing fluid, the biofilm is extremely difficult to completely remove and tends to quickly reestablish itself. Furthermore, the biofilm tends to impede the disinfectant action. Accordingly, the bacterial count in water delivered to a patient's mouth rapidly increases to unacceptable levels. Unfortunately, this problem was previously unrecognized by dental professionals. It is not an obvious problem, since most people would not associate an illness that they subsequently experienced with an infection caused by microorganisms delivered in water previously injected into their mouths during a dental procedure a week or two before. Because the bacterial infection problem associated with dental tool water lines has not been earlier recognized, there is not an available solution to the problem that is sufficiently low in cost to encourage dentists to employ it.